<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    


    <button type="button">输出</button>

    <script>
        var btn = document.querySelector('button')

        btn.addEventListener('click',function(){
            console.log('aaaaaaaaaaaaa')
            
        })
        
        btn.removeEventListener('click',function(){
                console.log('事件被移除')
            })
    </script>
</body>
</html>